Mercury tube switch



Nov. 17, 1936. c. H. LARsoN MERCURY TUBE SWITCH Filed April 24, 1935(bm-@WW M3071/ I,

Patented Nov. 17, 1936 PATENT oFFlcE MERCURY TUBE SWITCH` Carl H.Larson, Elkhart, Ind., assigner to The Adlake Company, a corporation ofIllinois Application. April 24, 1935, Serial No. 17,9%

'l Claims. (Cl. flitumilil This invention relates to mercury tubeswitches in which the level of the mercury is determined by the positionof a displacer and that is dependent upon a magnetic core in the tubesub= ject to a magnet and the principal object is to make it easy toinspect the electrodes and their relation to the mercury whileassembling the switch, and when it is in service. This is achieved byusing a very buoyant and transparent displacer of glass, for exampleassembling, carrying a magnetic core above the parts to be seen.Incidentally, this keeps the metal of the 'core from affecting themercury and contributes .to other advantages which will appear as thedescription is read in connection with the accom" panying drawing, inwhich Fig. l is a vertical section through one :form oi power'transierswitch embodying the invention, with the parts shown in the positionthey assume when the magnet is def-energized and the displacer isiioating in the mercury;

Fig. 2 is a section of the same switch with the parts in the positionthey assume when the 4magnet is energized and the displacer is lifted;

Fig. 3 is a perspective view oi the displacer and the magnetic core;

i Figs. 4, 5 and 6 are views similar to Figs. 1, 2 and 3, but disclosinga diferent form of power transier switch embodying the invention.

l3nt this drawing and the description are used for the purpose ofdisclosure only, and others will be able to make different forms andapply various features of the invention to use in other switches.

Thev mercury switch includes a glass tube or envelope Ill, pinch sealedat the bottom Il and sealed ofi at the top I2, after being given acharge of mercury I3 and a suitable gas iill, such as helium, 'heliumhydride, hydrogen, etc.

Three conductors, I4, I5 and I6, are sealed through the bottom, and thelast two are insulated from the mercury by sleeves IIl and I8, diierentheights beyond which they are exposed.

The displacer is a transparent tube I9 which,

in this power transfer switch, takes the form of an inverted test tube,or thimble, having a closedupper end and a wide open lower end 2|, thelatter receiving the conductor I5 and sleeve II in the position shown inFig. 1.

The magnetic core, or armature 22, of some ferrous material is a hollowcylinder having rounded hardened steel guides 23 pressed into- The coreis preferably made of exceptionally pure iron, such as, for example,Svea metal, sold in the United States by the Swedish iron and SteelCompany, of New York, but oi course other ferrous material will-beselected to suit conditions of service.

A spring til of piano wire, coated with imagu netic oxide of iron, ordegassed pure iron, is screwed into the bore 25 of the core and hasseveral turns 26 close together to bind it securely in the core. Theupper portion of the core is counter-bored at 2l, and the spring 24projects bey-ond the upper end to prevent the core from striking the topportion It? ci the glass envelope while the switch is being shipped orhandled.

another coil springA 2li extends across the bottom oi the tube ill aboutthe sleeve il, and acts as a cushion for the lower end 2l of thedisplacer tube is.

The lower end of the core 2i has a reduced hollow nipple into which theupper closed end 20 of the displacer is inserted. Ordinarily thefriction of a slight taper will be suicient to maintain the assembly,but the tube may be cemented in place with silica, if desired.

In order to permit mercury to escape from the bore of the armature afterthe switch has been on its side, diagonal cuts 30 are made in thearmature with a milling cutter, beginning at about the juncture of thenipple 29 with the main body of the armature.

l Should the armature be made split, as is sometimes done for use withalternating current, the cuts may be omitted.

The electromagnet associated with the Switch includes a coil 3l, alaminated yoke 32, preferably of Allegheny transformer steel, and polesleeves 33 of pure soft iron, such as Svea metal, held in place by ironclamps 34.

The mercury tube switch is adjustably held within the core by a splitring 35 of. spring brass located between the adjacent ends of the polesleeves 33, and frictionally holding the glass tube Ill.

VThe displacer I9, being transparent from the lower end of the nipple 29to the bottom 2|, the height of the charge of mercury in relation to theelectrodes formed by the exposed end of the conductors I-I and I5, canbe adjusted by sight during the assembly operation, and afterwards inuse the electrodes and the height of the mercury can be inspected at anytime by direct vision.

The displacer should be made of heat resisting glass of which there area numberon the market known as boro-silicate glass, Pyrex, etc., orwhere the cost will permit, it may be made of. quartz.

In Fig. 1 thev displacer, trapping gas within it, forces the mercuryaway from the exposed end of the conductors I5 and raises the levelabove the sleeve I9 and closes the circuit between the conductor Il andthe exposed end of the conductor I6.

Upon the magnet being energized, the armature lifts the displacer toabout the position shown in Fig. 2, the mercury rises about the exposedend of the conductor I5 and falls below the exposed end of the conductorI6, thereby opening the circuit from the conductor or to the conductorI6, and closing the circuit from the conductor I5 to the conductor I4. i

Such switches are used to transfer from one source of power to anotherand, of course, the one circuit must be broken before the other circuitis closed. That is easily accomplished with the switches here disclosedand at the same time the volumes are reduced to such a small extent thatvery little power is used to operate the switch.

As an example of dimensions, one form of switch that has been foundsatisfactory has a tube I0, 138 mm. long, 151/2 to 16 mm. insidediameter. The conductor I5 extends 27 mm. above the bottom of the tubeat the inside and is exposed for a length oi 5 mm. and the conductor I6extends 34 mm. above the bottom of the tube and is also exposed for 5mm.

'I'he armature is 1H inches long, f1; inches inside diameter, and thecounter bore is 1/2 inch in diameter for a depth of. H inches. Otherdimensions are in proportion.

In the form shown in Figs. 4, 5 and 6, a glass tube, or envelope 36, issimilar to the glass tube III, except that it has a lateral enlargement31 at the bottom to provide space for the conductor I5 by which means arelatively small tube serves for a three-electrode switch, and providesample clearance for all parts. I

'I'he displacer tube, or thimble, 38, is longe than the tube I9, and thecore, or armature 39, is a split sleeve telescoped over the displacerand provided with fingers 40 at its ends, making contact with the outersurface of the tube, or being spaced from it very slightly.

A spring 4I of degassed pure iron rits tightly over the upper end ot thethimble 38, and the tips of the fingers 4I) are wedged between theadjacent convolutions Vof the coil.

In assembly the armature and the spring are gotten into the positionshown in the drawing by a threading movement, the displacer tube isinserted from below and pressed upwardly while being turned, which hasthe effect of threading the coil onto it, where it remains securely bythe y clamping friction.

When the magnet is de-energized the parts assume the position shown inFig. 4, the displacer forcing the mercury away from the exposed end ofthe conductor I5 before it rises to cover the exposed end of theconductor IB.

When the magnet is energized, the parts assume the position shown inFig. 5, the circuit from the conductor I4 to the conductor I6 being rstbroken and then the circuit from conductor I 4 to conductor I5 closed.

It will be obvious to those skilled in the art that the constructionhere illustrated provides the necessary clearances with a minimumvolurne of mercury and a very small power consumption.

For alternating current service, the armature 39 is cold rolled steel,case hardened Vand ground or some similar material whereby the armaturerequires no guide and can be gotten very close to the magnet. For directcurrent service, soft iron should be used and guides provided, asexplained in the co-pending application of Gehrand and Larson, led April18, 1935, Serial Number 17,053.

I claim as my invention:-

1. In a. mercury tube switch, a tube, a conductor sealed through thebottom of the tube and provided with an electrode within the tube,mercury in the tube to co-operate with the electrode, a hollowtransparent displacer cooperating with the mercury and adapted to coverthe electrode and a hollow magnetic core carried by the displacer andarranged so that a side view of the electrode is possible through thetransparent displacer.

2. Ina mercury tube switch, a tube, a conductor sealed through thebottom of the tube and provided with an electrode within the tube,mercury in the tube to co-operate with the electrode, a tubulardisplacer substantially closed at its upper end adapted to telescopeover the electrodeA ing one of the conductors for a space above thebottom of the tube, a tubular displacer closed at its upper end andaligned with the last mentioned conductor whereby in one position itwill displace mercury from that conductor, and a magnetic core borne bythe displacer at all times above the mercury level.

4. In a mercury tube switch, a tube, conductors sealed through thebottom of the tube, mercury in the tube, an insulating sleevesurrounding each of the two conductors for a distance above the bottomof the tube, a transparent tubular displacer having a pocket open at itsbottom and adapted in one position to displace mercury from one of theconductors and a. magnetic core carried by the displacer above themercury level.

5. In a mercury tube switch, a tube, mercury therein, conductors sealedthrough the tube for co-operation with the mercury, a tubular displaceropen at its bottom to the mercury and closed above, and a magnetic corecarried by the displacer above the mercury.

6. In a mercury tube switch, a tube, mercury therein, conductors sealedthrough the tube for co-operation with the mercury, a displacercornprising a glass tube closed at the top and open at the bottom totrap gas above the mercury, and a magnetic core fixed to the displacerabove the mercury.

'7. In a mercury tube switch, a tube. conductors sealed through thebottom oi' the tube, mercury in the tube, an insulating sleevesurrounding one of the conductors for a distance above the bottom of thetube, a transparent tubular displacer open at its bottom and adapted totelescope over said one conductor, and a magnetic core carried by thedisplacer above the mercury level.

CARL H. LARSON.

